Reorganising data for -ranksum- test

[Sara Khan]

I wish to use the

 -ranksum-

command. My data are in the current format:

     +-------------------------------------------+
     | SkinT~d0   SkinT~d6   SkinT~d8   Skin~d10 |
     |-------------------------------------------|
  1. |     26.4         27       29.4       36.1 |
  2. |     49.7          .          .          . |
  3. |     60.4          1          .       13.6 |
  4. |     17.2       14.2       14.2        8.3 |
  5. |     34.4       26.6       15.4       51.5 |
     |-------------------------------------------|
  6. |        .          .          .          . |
  7. |        .          .          .          . |
  8. |     24.8          .       37.9       53.3 |
  9. |     16.6       88.2       81.2       47.9 |
 10. |      5.3        1.8        4.7        1.2 |
     |-------------------------------------------|
 11. |     16.6        2.4        3.6        4.1 |
 12. |        .       78.1       75.1       29.6 |
 13. |        .          .          .          . |
 14. |     29.6       30.2       49.1       13.6 |
 15. |     27.8       10.7        5.9       14.2 |
     +-------------------------------------------+

I would like the values of the second variable (SkinT~d6) to be placed immediately after the first variable (SkinT~d0) and a binary variable to indicate which group the values belong to. I would be grateful for any advice on how to do this.

[Nick Cox]

Possibly you see a reshape

help reshape

but you need an identifier variable first.

[Carlo Lazzaro]

Sara:
-help stack- might be what you're looking for.
PS: crossed in the cyberspace with Nick's reply, who interestingly highlights a different approach.